Recently, vehicle keyless systems have been widely used and various proposals for improving the convenience of such systems have been made.
In some vehicle keyless systems, different command signals are transmitted from a portable device depending on an operational mode of a key button.
For example, when the key button is normally operated, a command signal instructing vehicle door locking or unlocking is transmitted as a main signal, while when the key button is pressed for a long time (operated in a special mode), a command signal instructing door window opening or closing is transmitted as a sub signal.
Patent Literature 1 discloses a vehicle keyless system in which, when a key button of a portable device is pressed for a long time, the portable device performs RF transmission of a command signal, and an on-vehicle device having received the transmitted command signal performs LF transmission of a reply signal.